Typically, in multiple cylinder internal combustion engines, the timing between the camshaft and the crankshaft are fixed. However, in order to increase fuel economy and reduce harmful emissions emitted from the engine, the timing (or phase) of the camshaft relative to the crankshaft needs to be adjusted to optimize the engine for different operating conditions. As a result, phase shifting mechanisms have been developed to allow the rotational phase of the camshaft to vary relative to the crankshaft. In addition, sensors have been added along with marked camshaft data wheels and a crankshaft data wheel, to determine the rotational position and velocity of the camshaft and crankshaft which then signals to an onboard microprocessor. This then determines how much phase shift is needed for a given engine operating condition and activates the phase shifting mechanisms to accomplish the phase shift.
Another recent advance in engine technology, also for reducing harmful emissions and increasing fuel economy, is sequential fuel injection. In order to accomplish this, an additional sensor and camshaft sensing wheel has been added to read the cylinder identification, which locates the top dead-center position of the first cylinder. With this information electronically transmitted to an onboard computer, the computer can electronically transmit a signal to the individual fuel injectors to optimize the timing of the injection of fuel into each individual cylinder.
With the addition of these and other recent advancements, it has become important to have a crankshaft sensor to determine the ignition timing for each cylinder. In case of a problem with a crankshaft sensor, an additional redundant sensor on the crankshaft has typically been used to back-up the first sensor in case of failure.
In order to reduce the number of sensors, marked camshaft data wheels and computer inputs with a resulting reduction in cost and improved reliability, and still accomplish these functions simultaneously, a system which integrates these functions is needed. Then, one integrated system can accomplish camshaft phase shifting, sequential fuel injection, ignition operation and also ignition operation when the crankshaft sensor fails without the need for a redundant crankshaft sensor.